cat -n <file> | sort -k 2 | uniq -f 1 | sort -n | cut -f 2-

delete duplicate lines from a file and keep the order of the other lines

i wanted to delete all duplicate lines from .bash_history and keep the order of the other lines. the command cat's the file and adds line numbers, then sorts by the second column. afterwards uniq omits repeated lines, but skips the first field (the line number). then it sorts by the line numbers and at the end cuts the numbers off.

4
By: fpunktk
2010-01-21 18:55:58

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What Others Think

The first chain of commands will work better than second proposal (awk) for the bigger files. I've tested it on the file with 3000000 lines (1000000 unique lines) and awk was 6 times slower (and consumed more memory). awk will be faster for a smaller files tho.
zabuch · 434 weeks and 6 days ago
with this code, how would you keep duplicates ONLY and Delete the rest?
y2j164 · 416 weeks and 2 days ago
to delete single lines and keep one of each duplicate line, just add the -d option to uniq. e.g. cat -n <file> | sort -k 2 | uniq -f 1 -d | sort -n | cut -f 2-
fpunktk · 414 weeks and 2 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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